The present invention relates to sundials. The present invention is a form of horizontal sundial showing standard time and incorporating a gnomonic projection map.
Most horizontal sundials indicate local solar time (a system of time measurement abandoned long ago). It is a principal object of the present invention to provide a sundial that can be used, like a modern clock or watch, to find standard time to the nearest minute.
The present invention meets such object by automating on computer the construction of the circle or other trace showing the time and incorporating this with a gnomonic projection map. A gnomon, preferably made of metal wire (e.g. nitinol or stainless steel), not only indicates by its shadow the time on the hour scale but also marks the point of midday on the map and is further configured by means of a bead on the wire to indicate the place where the Sun is directly overhead. Since the height of the Sun varies with the seasons, the invention can be configured so that the bead's shadow can be used to highlight special dates (anniversaries, birthdays, & etc.) marked on the map between the Tropics of Cancer/Capricorn. Other scientific, commercial (practical) and versatile aspects of the invention are described below.
Although a computerized map-projection program became available in the 1970s for cartographic purposes, due to cost its availability was restricted to universities, corporations, and government institutions. Map-projection software programs (e.g. Geocart introduced in 1993) contributed to cartography but the relevance of the computer modeling of the gnomonic projection to the construction of a sundial has not been recognized or implemented.
It is a principal object of the invention to provide a sundial with standard time display of high accuracy that can be manufactured on a commercially viable basis while allowing customization to any given location on Earth. Further objects are to show where noon occurs and the sun is overhead.
Other objects, features and advantages will be apparent from the following detailed description of preferred embodiments taken in conjunction with the accompanying drawings in which: